Cartilage and Bone Structure and Function

Bones

Bone Characteristics Vascular (has own blood supply) Regenerates well Contains calcium and hydroxyapatite Forms mostly after birth Is not flexible

Bone Cells Osteoblast (makes bone) Osteocyte (mature bone cell) Osteoclast (reabsorbs bone)

Formation of Endochondral Bone Hyaline cartilage develops in the general shape of the future bone. Periosteum forms on the outside of the developing bone. Osteoblasts deposit bony tissue in place of disintegrating cartilage.

Types of Ossification Primary starts in diaphysis from cartilage Secondary starts in epiphysis from cartilage

Types of Bones Long Bones Arms and legs Sesamoid Bones Develop inside tendons and near joints Flat Bones Skull bones and scapula Irregular Bones vertebrae

Cartilage What are the three types of cartilage? Hyaline cartilage (most of the joints) Fibrocartilage (vertebral discs, pubic symphysis) Elastic cartilage (ears) Where in the body can each of these three types of cartilage be found? What type of cartilage does an embryonic skeleton have? Hyaline

Cartilage Characteristics Avascular (no blood supply) Does not regenerate well Contains no calcium or hydroxyapatite Begins conversion to bone before birth Is flexible

Joint Disorders and Joint Injuries Structure of joints makes them prone to traumatic stress Function of joints makes them subject to friction and wear Affected by inflammatory and degenerative processes Sprains – ligaments reinforcing a joint are stretched or torn Dislocation – occurs when the bones of a joint are forced out of alignment Torn cartilage – common injury to meniscus of knee joint

Inflammatory and Degenerative Conditions Bursitis – inflammation of a bursa due to injury or friction Tendonitis – inflammation of a tendon sheath Arthritis – describes over 100 kinds of joint-damaging diseases Osteoarthritis – most common type – “wear and tear” arthritis Rheumatoid arthritis – a chronic inflammatory disorder Gouty arthritis (gout) – uric acid build-up causes pain in joints Lyme disease – inflammatory disease often resulting in joint pain; Lyme disease is caused by a bacterium and is transmitted to humans by the bite of infected blacklegged ticks. Typical symptoms include fever, headache, fatigue, and skin rash. If left untreated, infection can spread to joints, the heart, and the nervous system.

Osteoporosis: loss of minerals Figure 6.15 Normal Bone Osteoporosis

Stages of Healing a Fracture Figure 6.14 Blood escapes Fibrous callous Spongy Bone callous Osteoclasts remove excess bone

Categories of Fractures Simple: Skin is not broken Compound: Bone sticks out through skin, often gets infected Complete: Both sides of diaphysis broken through Incomplete: One side of diaphysis is broken Stress: Just a crack in the surface

Types of Fractures Comminuted Compression Spiral Epiphyseal Depressed Greenstick

Table 6.1